On Magneto-electric Induction in Liquids and Gases. 143 



March 8. — Dr. J. Dallon Hooker, C.B., President, iu the Chair. 



The following paper was read : — 



" On Magneto-electric Induction in Liquids and Gases. — Part I. 

 Production of Induced Currents in Electrolytes." By J. A. Fleming, 

 B.Sc. (Lond.). 



This paper contains an account of an experimental inquiry 

 into the production of induced currents in liquids by magneto- 

 electric induction. Earaday examined one such case of induction, 

 in which a conducting liquid was used as a secondary circuit. He 

 coiled round the armature of an electromagnet an india-rubber tube 

 filled with dilute sulphuric acid, and found, on making and breaking 

 the primary circuit, the induced currents generated in it, as in the 

 case of metallic conductors ; but he could not obtain any effect 

 when brine, sulphuric ^cid, or other solutions were rotated in 

 basins oyer a magnet, or enclosed in tubes and passed between the 

 poles. He failed also to detect any magneto-electric current in 

 water flo\Aing across the earth's lines of magnetic force (viz. in 

 the river Thames). 



Since the reason for these negative results is not at once obvious, 

 it seemed desirable to repeat and extend them to other cases, so 

 that, if possible, the analogy of electrolytic with solid conductors 

 might, in respect to magneto-electric induction, be completed. In 

 addition, the subject involves the interesting question of the 

 magneto-electric phenomena accompanying the flow of ocean- 

 currents and other large masses of water. 



Three cases of induction in liquids flowing iu a magnetic field 

 or traversed by lines of magnetic force have been examined. 



1. Production of induced current in a liquid stream flowing uni- 

 formly in a constant magnetic field. — When a stream of conducting 

 fluid flows vertically down between the poles of a magnet a 

 transverse current is produced in a direction at right angles to the 

 lines of force and line of flow. This was obtained in the follow- 

 ing way : — A glass tube, about 200 centims. long and 2 centims. 

 w^de, had platinum plates 15 millims. wide placed along its inside 

 and at opposite sides, w\t\i their lengths parallel to the axis of the 

 tube. Platinum wires welded to these plates were sealed through 

 the glass. The plates were curved to lie closely against the sides 

 of the tube. This tube was placed vertically between the poles of 

 a large electromagnet, the line joining the platinum plates being 

 at right angles to the line of the poles. 



To the upper end of the tube was attached another, leading to a 

 reservoir of dilute sulphuric acid placed high above the floor ; to 

 the lower end a tube leading to a receptacle on the floor. The 

 platinum plates were then connected with a distant galvanometer. 

 When the magnet was not excited, no flowing of the liquid had 

 any effect on the galvanometer ; but when it was excited, at the 

 moment the flow began the galvanometer showed a deflection of 

 10° to 15°. Since the only part of the galvanometer circuit in 

 motion is the liquid, this deflection was due to the magneto-electric 



